New data will be obtained on the mechanism of proton transfer reactions. We will study intramolecular proton transfer to learn about tunneling of protons through a barrier. The dynamics of a proton transfer in the vicinity of a proton donor or acceptor will be studied to understand the mechanism by which a proton moves through the donor-solvent interface. We hope to confirm or deny the presence of a solvent cage and an electrostatic cage that have been postulated to play an important role in proton transfer reactions. The application of high pressure coupled with changes in the temperature will be used to alter the hydrogen bond structure of water. This should provide important data on how the water structure effects the anomalously high diffusion of protons in water. Molecules which undergo excited state pK changes will be irradiated with a picosecond laser. Time resolved absorption and fluorescence will be used to monitor the proton dynamics.